What is a best way to organize my own kitbash library?
There is an ongoing project for future Blender 2.8X called Asset Engine to improve the asset and library management features of Blender.

It will feature local file system based storage of assets with tagging and organization features, and previewing capabilities as stated in the Wiki.

It is unknown at this point when it will be ready and integrated into official releases, however it is unlikely to make it into the first official 2.80 release.

At the moment you can currently organize your assets as group instances or even individual  objects and generate datablock preview images for them. You can then browse the assets using Blender's built in file browser with thumbnail previewing capabilities-